ABSTRACT: Each year, more than 24,000 women die from colorectal cancer, which makes it the third leading cause of cancer death in women after lung cancer and breast cancer. However, screening tests are underused for many segments of the population and are ordered in a manner inconsistent with guidelines. The primary goal of colorectal cancer screening is to reduce mortality through the reduction of advanced disease. The American College of Obstetricians and Gynecologists recommends colonoscopy for colorectal cancer screening every 10 years for average-risk women beginning at age 50 years and at age 45 years for African American women. The American College of Obstetricians and Gynecologists recommends colonoscopy every 10 years as the most effective screening modality. Every screening method has advantages and limitations, which ultimately depend on the quality of the screening test, patient adherence, screening guidelines, and access to timely and appropriate follow-up. Colorectal cancer screening methods should be discussed with patients to identify the method they are most likely to accept and complete.
Conclusions and Recommendations
Based on the following information, the American College of Obstetricians and Gynecologists (the College) provides these conclusions and recommendations:
- Colorectal cancer screening for average-risk women should begin at age 50 years.
- Colorectal cancer screening for African American women should begin at age 45 years.
- The College supports stopping routine screening at age 75 years.
- The College recommends colonoscopy every 10 years as the most effective screening modality.
- Colorectal cancer screening methods should be discussed with patients to identify the method they are most likely to accept and complete.
- Tests that detect early colorectal cancer and adenomatous polyps, the most effective of which is colonoscopy, should be encouraged.
- Abnormalities found with any other screening method necessitate referral for diagnostic colonoscopy.
- Digital rectal examination for in-office single-stool guaiac fecal occult blood testing (gFOBT) for colorectal cancer screening is ineffective and not recommended.
- Every screening method has advantages and limitations, which ultimately depend on the quality of the screening test, patient adherence, screening guidelines, and access to timely and appropriate follow-up.
Approximately 70,000 women in the United States develop colorectal cancer each year. Colorectal cancer is diagnosed in more women than any individual gynecologic cancer. Each year, more than 24,000 women die from colorectal cancer, which makes it the third leading cause of cancer death in women after lung cancer and breast cancer (1). Despite consensus among health care organizations about the value of screening for colorectal cancer, a recent study reported that only approximately 65% of respondents (U.S. women aged 50–75 years) have been screened using colonoscopy or sigmoidoscopy in the past 10 years or fecal occult blood test within the past year (2). It has been calculated that if 90% of the population were screened as recommended, 310,000 lifetime quality-adjusted life years would be saved (3). However, screening tests are underused for many segments of the population and are ordered in a manner inconsistent with guidelines—many physicians continue to recommend that screening begin before age 50 years or be repeated too frequently (4).
The purpose of this document is to review the available methods and recommended screening guidelines for women at average risk of colorectal cancer to enable the obstetrician–gynecologist to appropriately and adequately counsel patients about colorectal cancer screening (see Table 1). The primary goal of colorectal cancer screening is to reduce mortality through the reduction of advanced disease. Randomized trials have demonstrated reductions in mortality associated with early detection of colorectal cancer as well as with removal of adenomatous polyps. The detection of early-stage adenocarcinomas and the detection and removal of adenomatous polyps can be achieved by colorectal cancer screening (5). Women who are at increased risk of colorectal cancer are not included in these screening guidelines developed for women at average risk (see Box 1 for risk factors). For women at increased risk, earlier and more frequent screening starting at age 40 years, or 10 years younger than the age at which colorectal cancer was diagnosed in the youngest affected relative, has been recommended by the American College of Gastroenterology and the Institute for Clinical Systems Improvement (6, 7). Obstetrician–gynecologists should recognize that endometrial cancers may be a hallmark of women at increased risk of genetically linked types of cancer (eg, hereditary nonpolyposis colorectal cancer or Lynch syndrome) (8).
Table 1. Screening Guidelines for the Early Detection of Colorectal Cancer and Adenomas for Average-Risk Women Aged 50 Years and Older*
|Test That Detects
||Key Issues for
||Every 10 years
- Adenoma removal can possibly prevent colorectal cancer.
- Complete bowel preparation is required.
- Conscious sedation is used in most centers; patients will miss a day of work and will need a chaperone for transportation from the facility.
- Risks include perforation, bleeding, and death, which are rare but potentially serious; most of the risk is associated with polypectomy.
- Limitations include significant variability in quality and performance and dependency on the operator’s skill.
|83% reduction in mortality
|Flexible sigmoidoscopy with insertion to 40 cm or to splenic flexure
||Every 5 years
- Complete or partial bowel preparation is required.
- Sedation usually is not used, so there may be some discomfort during the procedure.
- The protective effect of sigmoidoscopy is limited primarily to the portion of the colon examined.
- Patients should understand that positive findings on sigmoidoscopy usually result in a referral for colonoscopy.
- Complications include colonic perforation, even if no biopsy or polypectomy is performed; this occurs in fewer than 1 in 20,000 examinations.
|60-70% reduction in mortality from left colon lesions
||Every 5 years
- Complete bowel preparation is required.
- If patients have one or more polyps larger than 6 mm, colonoscopy will be recommended; if same-day colonoscopy is not available, a second complete bowel preparation will be required before colonoscopy.
- Risks of CTC are very low; rare cases of perforation have been reported.
- Significance of incidental extracolonic findings is not clear.
- Increased lifetime cumulative radiation risk needs further evaluation.
|gFOBT with high sensitivity for cancer
- Depending on manufacturer’s recommendations, the test requires two samples from each of three consecutive bowel movements at home; a single sample of stool gathered during a digital examination in the clinical setting is not an acceptable stool test and should not be done.
|15-33% reduction in mortality
|FIT with high sensitivity for cancer
- A positive test result is associated with an increased risk of colon cancer and advanced neoplasia; colonoscopy should be recommended if the test result is positive.
- If the test result is negative, the test should be repeated annually.
- Patients should understand that one-time testing is likely to be ineffective.
|74% reduction in mortality
|sDNA with high sensitivity
- An adequate stool sample must be obtained and packaged with appropriate preservative agents for shipping to the laboratory.
- The unit cost of the currently available test is significantly higher than other forms of stool testing.
- If the test result is positive, colonoscopy will be recommended.
- If the test result is negative, the appropriate interval for a repeat test is uncertain.
Abbreviations: CTC, computed tomography colonography; FIT, fecal immunochemical test; gFOBT, guaiac-based fecal occult blood test; sDNA, stool DNA test.
*These options are acceptable choices for colorectal cancer screening in average-risk adults beginning at age 50 years and at age 45 years for African Americans. Because each of these tests has inherent characteristics related to prevention potential, accuracy, costs, and potential harms, individuals should have an opportunity to make an informed decision when choosing one of these options. In the opinion of the Guidelines Development Committee (of the American Cancer Society, the U.S. Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology), colon cancer prevention should be the primary goal of colorectal cancer screening. Tests that are designed to detect early cancer and adenomatous polyps should be encouraged if resources are available and patients are willing to undergo an invasive test.
†Computed tomography colonography currently is not recommended by the U.S. Preventive Services Task Force, may not be covered by some insurance plans, and currently is not covered under Medicare.
Data from Levin B, Lieberman DA, McFarland B, Andrews KS, Brooks D, Bond J, et al. Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the U.S. Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. Gastroenterology 2008;134:1570–95; National Cancer Institute. Colorectal cancer screening (PDQ®). Available at: http://www.cancer.gov/cancertopics/pdq/screening/colorectal/HealthProfessional. Retrieved April 9, 2014; and Telford JJ, Levy AR, Sambrook JC, Zou D, Enns RA. The cost-effectiveness of screening for colorectal cancer. CMAJ 2010;182:1307–13.
The College recommends initial colonoscopy for colorectal cancer screening for average-risk women beginning at age 50 years and at age 45 years for African American women, with follow-up colonoscopy every 10 years as the most effective screening modality. The College supports stopping routine screening at age 75 years. Reasons for the higher incidence rate of colorectal cancer in African Americans are unclear but are associated with variability in screening rates, lower use of diagnostic testing, and lifestyle factors (eg, nutrition and rates of physical activity) (9).
The College has developed practical guidance for the obstetrician–gynecologist by recommending colonoscopy as the preferred method of screening because it allows for a full examination of the colon and rectum in one session. It also allows the practitioner to perform a biopsy or polypectomy, if indicated. Colorectal cancer screening methods should be discussed with patients to identify the method they are most likely to accept and complete. Understanding the advantages and limitations of each screening method is necessary to counsel women adequately. Tests that detect adenomatous polyps and early colorectal cancer, such as colonoscopy, should be encouraged. However, all methods described in this Committee Opinion are acceptable options to screen for colorectal cancer. Abnormalities found with any other screening method necessitate referral for diagnostic colonoscopy. Every screening method has advantages and limitations, which ultimately depend on the quality of the screening test, patient adherence, screening guidelines, and access to timely and appropriate follow-up. Additionally, increased sensitivity by health care providers to patients’ behaviors, feelings, cultural differences, and attitudes can result in increased patient and health care provider satisfaction.
Box 1. Risk Factors for Colon Cancer ⇦
—lack of regular physical activity
- Inflammatory bowel disease, Crohn disease, or ulcerative colitis
- A personal or family history of colorectal cancer or colorectal polyps
- A genetic syndrome such as familial adenomatous polyposis or hereditary nonpolyposis colorectal cancer (Lynch syndrome)
- Lifestyle factors that may contribute to an increased risk of colorectal cancer include
—low fruit and vegetable intake
—a low-fiber and high-fat diet
—overweight and obesity
Data from Centers for Disease Control and Prevention. Colorectal (colon) cancer: what are the risk factors? Available at: http://www.cdc.gov/cancer/colorectal/basic_info/risk_ factors.htm. Retrieved April 16, 2014.
Colorectal Cancer Screening Tests
Colorectal cancer screening tests may be divided into two categories: 1) cancer prevention and 2) cancer detection. Cancer prevention testing or imaging studies include the ability to detect premalignant lesions, such as adenomas and polyps; however, these tests also may detect colon cancer. Cancer detection testing primarily relies on detection of blood in the stool and may have a lower sensitivity for polyps or cancer.
Tests That Detect Adenomas and Colorectal Polyps
The College recommends colonoscopy for colorectal cancer screening every 10 years for average-risk women beginning at age 50 years and at age 45 years for African American women. Colonoscopy should allow for the mucosal inspection and appropriate biopsy of the entire colon from the dentate line to the appendiceal orifice. Colonoscopy gives access to right-sided lesions, which comprise a considerable proportion (65%) of advanced colorectal neoplasia in women that would be missed by other screening methods, such as sigmoidoscopy (10). Twenty-year follow-up data from 88,902 participants in the Nurses’ Health Study and the Health Professionals Follow-up Study demonstrated a decrease in incidence of and mortality from colorectal cancer after screening sigmoidoscopy or colonoscopy. Only colonoscopy resulted in a reduction in proximal colon cancer (11). In one study, it was shown that the incidence of colorectal cancer was reduced by 76–90% among individuals undergoing colonoscopy with polypectomy compared with individuals in a general population registry (12).
Although colonoscopy remains the standard method for detecting colorectal pathology, it may not detect all polyps or cancer. As noted by the U.S. Preventive Services Task Force, studies in which the same patient is studied twice via colonoscopy and studies comparing colonoscopy with computed tomography colonography demonstrate that colonoscopy may miss even polyps larger than 10 mm and colorectal cancer (13). Limitations of colonoscopy include cost, dietary preparation for the procedure, inconvenience of the bowel preparation required of the patient, the necessity of a chaperone for transportation because of sedation, missing lesions, and the risk of serious complications. One study found 2.8 serious complications (including perforations, hemorrhage, diverticulitis, cardiovascular events, severe abdominal pain, and death) per 1,000 procedures (confidence interval [CI], 1.5–5.2 per 1,000 procedures; test for heterogeneity; P=.13) (14).
The effectiveness of the colonoscopy is dependent upon the thoroughness of the bowel preparation and the skill of the endoscopist. The endoscopist should have the ability to sample or remove precancerous lesions (15). Measures for improving the quality and cost-effectiveness of colonoscopy as a colorectal cancer screening test include adequate bowel preparation, documentation of cecal intubation (passage of the colonoscope tip to a point proximal to the ileocecal valve so that the entire cecal caput, including the medial wall of the cecum between the ileocecal valve and appendiceal orifice, is visible ), reporting of adenoma detection rates, withdrawal times (the time from cecal identification to withdrawal of the scope from the anus) of at least 6 minutes, and effective removal of all polyps greater than 5 mm in size (6).
Flexible sigmoidoscopy is a test that involves the insertion of a thin, flexible tube into the rectum. The recommended interval between normal flexible sigmoidoscopy with depth of insertion to 40 cm or to the splenic flexure is every 5 years. This procedure is associated with a 60–80% reduction in colorectal cancer mortality for the area of the colon within its reach. This protective effect of a reduction in the incidence of distal colorectal cancer persists for up to 16 years (17). Two large screening studies indicate that if a patient has an adenoma of any size in the distal colon, she has a twofold or higher risk of proximal advanced neoplasia compared with patients with hyperplastic polyps or no polyps in the distal colon (18, 19). Flexible sigmoidoscopy is technically easier, requires less preparation, can be performed without sedation, and has a lower risk of complications compared with colonoscopy. However, it is limited to examining the most distal portion of the colon and will miss a significant number of right-sided colonic lesions, particularly in women and African Americans (10, 20). Positive findings usually will require referral for diagnostic colonoscopy. Because of these limitations, the combination of yearly, high-
sensitivity gFOBT or fecal immunochemical testing (FIT) (see “Tests That Primarily Detect Cancer”) with flexible sigmoidoscopy every 5 years may be preferable to either method alone (21).
Tests That Primarily Detect Cancer
High-Sensitivity Guaiac and Fecal Immunochemical Testing
High-sensitivity guaiac testing and FIT are noninvasive tests that detect occult blood in the stool that could be from polyps larger than 1 cm or cancer disrupting the mucosal barrier (5). (Any reference to gFOBT in this document implies high-sensitivity testing.) Colorectal cancer screening with gFOBT or FIT should be performed on an annual basis. High-sensitivity guaiac testing for occult blood is to be distinguished from older, conventional stool guaiac testing, which is less sensitive and, therefore, less reliable as a screening test and should not be used. The high-sensitivity guaiac-based tests rely on a peroxidase reaction to heme. Dietary restrictions to avoid animal sources of heme as well as limitations on the use of aspirin or nonsteroidal antiinflammatory drugs to avoid upper intestinal sources of blood are required. Fecal immunochemical testing specifically detects globin rather than heme and is more likely to detect colon bleeding rather than upper gastrointestinal bleeding (22). Fecal immunochemical testing is more specific than gFOBTs (the more traditional guaiac tests) because gFOBTs respond only to human globin and do not detect upper gastrointestinal bleeding (because the globin is digested in transit) or foods with peroxidase activity. Diet and medication restrictions are not required for FIT. Three large randomized control trials have shown that patients screened with gFOBT have cancer detected at an earlier and more curable stage compared with unscreened patients (5). In a meta-analysis of FIT, the pooled sensitivity was 0.79 (95% CI, 0.69–0.86) and specificity was 0.94 (CI 0.92–0.95) (23).
High-sensitivity guaiac tests typically require two samples from each of three consecutive bowel movements at home (5). The optimal number of FIT samples is unclear, but two samples may be superior to one. Fecal occult blood testing of a single stool sample from a rectal examination performed during an office visit is not adequate for the detection of colorectal cancer and should not be performed. In one study, the sensitivity of a single stool sample for fecal occult blood testing obtained during an office visit by digital rectal examination was 4.9%, compared with 23.9% for the recommended at-home fecal occult blood testing series (24).
Although gFOBT and FIT are the least invasive colorectal cancer screening methods, they have limitations. Both of these methods require samples obtained by the patient at home using a kit that must be returned for analysis. Another limitation of these tests is poor-quality screening practices, such as the use of in-office rather than at-home tests and inappropriate follow-up of positive test results, which may affect mortality rates (25). Health care providers should understand that gFOBT and FIT are less likely to detect cancer compared with the invasive tests and must be repeated annually to be effective. Positive test results with gFOBT or FIT require a diagnostic workup with colonoscopy to examine the entire colon. Digital rectal examination for in-office single-stool gFOBT for colorectal cancer screening is ineffective and not recommended.
Computed Tomography Colonography
Computed tomography colonography has been referred to as “virtual colonoscopy” in the lay press. Computed tomography colonography requires bowel preparation similar to colonoscopy. A 2011 meta-analysis of prospective, randomized trials and cohort studies comparing computed tomography colonography with colonoscopy demonstrated good sensitivity for computed tomography colonography for (advanced) adenomas greater than or equal to 10 mm; for (advanced) adenomas greater than or equal to 6 mm, sensitivity was somewhat lower (26). The potential harm from the evaluation of incidental extracolonic findings and the lifetime cumulative radiation risk must be considered. Because computed tomography colonography is an imaging examination, screening programs should consider offering same-day colonoscopy to eliminate a second bowel preparation for the patient. Radiologists experienced in the evaluation of this modality may not be widely available. This test currently is not recommended by the U.S. Preventive Services Task Force, may not be covered by some insurance plans, and currently is not covered under Medicare. Computed tomography colonography is listed as an option for screening by the American College of Gastroenterology and by the joint guideline of the American Cancer Society, the U.S. Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology (5, 6).
Fecal DNA Testing
Fecal DNA testing detects genetic mutations associated with colorectal cancer. Adenoma and carcinoma cells that contain neoplastic changes are shed into the lumen of the large bowel and eliminated with feces. Because there is no single gene mutation present in the cells of every adenoma or adenocarcinoma, a multitargeted DNA assay is necessary. In a prospective trial, the fecal DNA test was found to be more sensitive than gFOBT in detecting precancerous and cancerous colonic lesions in individuals at average risk of developing colorectal cancer (27). Fecal DNA tests are evolving, and no test is widely used; however, these tests have the potential to be highly specific. This test currently is not recommended by the U.S. Preventive Services Task Force.
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